A United Nations human rights expert says video footage from the final days of the Sri Lankan war proves that war crimes did take place.

Christopher Heyns, the U.N. investigator on extrajudicial killings, says what is reflected in the video are crimes of the highest nature.

The video, obtained by Britain's Channel 4 in 2009, shows blindfolded prisoners being shot at close range by what are believed to be Sri Lankan army troops.

Heyns told the U.N. Human Rights Council Monday that he examined the video along with a technical and forensic expert to determine its authenticity.

Sri Lankan authorities have rejected his findings.

More than 7,000 civilians are believed to have died during the Sri Lankan army's final offensive against the Tamil Tigers. At least 80,000 civilians are estimated to have been killed during the 25-year civil war that began in 1983.